Field of the Invention
Embodiments of the present invention generally relate to a method and apparatus for post chemical mechanical polishing (CMP) of semiconductor substrates.
Description of Related Art
In the process of fabricating modern semiconductor integrated circuits (ICs), it is necessary to develop various material layers over previously formed layers and structures. However, the prior formations often leave the topside surface topography unsuitable for subsequent layers of material. For example, when printing a photolithographic pattern having small geometries over previously formed layers, a shallow depth of focus is required. Accordingly, it becomes essential to have a flat and planar surface, otherwise, some of the pattern will be in focus while other parts of the pattern will not. In addition, if the irregularities are not leveled prior to certain processing steps, the surface topography of the substrate can become even more irregular, causing further problems as the layers stack up during further processing. Depending on the die type and the size of geometries involved, the surface irregularities can lead to poor yield and device performance. Consequently, it is desirable to achieve some type of planarization, or polishing, of films during IC fabrication.
One method for planarizing a layer during IC fabrication is chemical mechanical polishing (CMP). In general, CMP involves the relative movement of the substrate against a polishing material to remove surface irregularities from the substrate. The polishing material is wetted with a polishing fluid that typically contains at least one of an abrasive or chemical polishing composition. This process may be electrically assisted to electrochemically planarize conductive material on the substrate.
Once polished, the semiconductor substrate is transferred to a series of cleaning modules that remove the abrasive particles and/or other contaminants that cling to the substrate after polishing. The cleaning modules must remove any remaining polishing materials before they can harden on the substrate and create defects. These cleaning modules may include, for example, a megasonic cleaner, a scrubber or scrubbers, and a dryer.
Although present CMP cleaning modules have been shown to be robust and reliable systems, next generation devices have increased particle and defect reduction requirements. Meeting these requirements on current post CMP cleaning modules tends to result in high particle loading of brushes used in the scrubbers. This particle loading is particularly high on substrates with exposed metal layers as well as for certain slurries used in oxide processes. The impact of lower brush service life is undesirable and may also result in a greater number of defects found on the substrate surfaces, particularly at the edge or the bevel locations.
Therefore, there is a need in the art for an improved substrate cleaning module.